This invention relates to a fire alarm or similar system, and more particularly to a microprocessor-based system in which serial synchronous power transmission and data communication are provided between a central station or panel and groups of terminal units; such system functioning, by means of independently operable loop controllers, to signal or indicate alarm conditions and the like so that supervisory personnel can be adequately informed of hazardous conditions.
ln a fire alarm system of the type just described, groups of terminal units are addressed by a so-called polling routine so that a microprocessor in the respective independent loop controller can determine the alarm states, if any, of its terminal units on a continuous basis. Thus, each of the terminal units, for example, 126 units on each of seven loops or lines, can be addressed cyclically, e.g., once every several seconds or so by its respective loop controller. If a given unit, during any cycle, is determined to be in the alarm state, then that information is communicated to the respective loop controller, and therefrom to a master controller so that a warning to supervisory personnel can be given.
When one or more units are found to be in alarm, the information is displayed on the central control panel. Such information is also printed out by a printing device. Meanwhile, information is obtained by the loop controller, for example, as to the type of terminal unit that is in the alarm state, and its location. Moreover, the loop controller upon receiving notification of an alarm status, sends a command to the particular terminal unit in alarm to illuminate its light emitting device so that personnel stationed nearby may precisely locate the outbreak of fire.
A fuller understanding of the operation of such a fire alarm system will be gained as a description of a detailed embodiment of the present invention proceeds. At that time, reference will be made to FIG. 1, in which the context of the invention is depicted, such context being a known fire alarm system of the type just described.
Accordingly, it is a fundamental object of the present invention to provide a city tie line arrangement whereby municipal fire authorities may be notified on a selective basis as to particular conditions that exist calling for the services of such authorities.
Another object is to make the connection of the city tie line completely programmable by the user such that he may determine by use of an interface which conditions or situations should call for notification of municipal fire authorities.